This invention relates to seat backs, and in particular to the core which generally defines its shape and characteristics. This core will generally be upholstered or sheathed in some way, but how the seat back supports the user and responds to his movements is dictated by the core.
Between the extremes of a rigid seat back and a fully upholstered one with internal springs, there are backs with a basic shape against which a user's back will fit comfortably but which will flex to a certain extent when the user moves, in effect trying to accommodate to a different posture. They will also change shape a bit between users of different physique.
One particular characteristic is the forward bow of the central part of the seat back, which gives support to the user's lumbar region. It has been recognised that it is desirable for the shape of this bowed part to be adjustable and there have been various proposals for altering this shape by some control mechanism. That is, the user can turn a knob, press a switch, or otherwise initiate some mechanical action that will pull or push the seat back into a different configuration. These may well work quite satisfactorily, but they make for complexity and therefore extra cost, and the user's control, if reasonably accessible, can spoil the otherwise “clean” lines of the seat.
It is the aim of this invention for the core of a seat back to be so constructed that it will accommodate well to different users and to different positions of users, while maintaining comfortable support, without extraneous control devices.